Various portable imaging systems have been proposed to image the posterior of human eyes (fundus camera) over the years. Some of the cameras are designed with the front of their objective lens contacting the cornea of the patients, while others are for non-contact operation. The contact type of fundus cameras exhibits the advantage of having much wider field of view and with easier alignment for operator. Certainly the required extra effort in sterilization and discomfort to patients are the clear short comes of this type of camera. Due to the unique optical path for projecting light through the opening of the iris and crystal lens of the eye, the image quality, in terms of contrast and color saturation, of wide field fundus camera is often inferior to that from narrow field non-contact cameras. In particular, the images often exhibit a layer of strong haziness due to the scattering of illumination light against the retina in background for patients with dark pigmentation in the eyes. In the prior art, a portable contact type of fundus camera is proposed where the hand held imaging capturing unit is separated from the light source and the rest of bulky electronics. An optical cable is used to transmit light from light source into the hand held unit, while the captured images are sent to the computer through an electrical cable. A movable cart is proposed to house the light source, computer, monitor, printer and power conditioner, etc. However, from the user's perspective, the use of the heavy cables makes precision adjustment of camera and handling of the imaging unit rather difficult. The heavy weight of the cart carrying the computer and all of accessories also makes the system difficult to move from within the hospitals, and almost impossible to transport between hospitals.
The need for a portable digital imaging device, which utilizes the advanced features of wireless data transmission and high computing power of mobile computing devices, is generating interest for the next generation of medical imaging devices. Such portable and wireless imaging devices will use miniature cameras and solid state lighting technology to achieve the significant reduction in size while maintain the performance against the desk-top type of imaging systems.